Thriving on Our Changing Planet A Decadal Strategy for Earth Observation from Space (2018) / Chapter Skim
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7 Weather and Air Quality: Minutes to Subseasonal
7 Weather and Air Quality: Minutes to Subseasonal
Pages 296-347
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There are numerous scientific, computational, and observational challenges associated with achieving such an integrated weather and air quality prediction system, but the societal benefits associated with more skillful weather forecasts across all lead times would truly be transformative. The Panel on Weather and Air Quality: Minutes to Subseasonal identified 10 primary science questions and quantified objectives to address these challenges, all of which will require observations from both research and operational satellite systems.
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will be needed to constrain these models as they become capable of explicitly resolving cloud microphysical processes at the convective updraft scales. This collective of new observations will lead to improved weather forecasts -- namely, by improving the initialization (through data assimilation)
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W-1a. Determine the effects of key boundary layer processes are integral to the air-surface (land, ocean, on weather, hydrological, and air quality forecasts at minutes to and sea ice)
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These fundamental science questions can be addressed only with advanced capabilities in observations, modeling and data assimilation systems, instrument platforms, and computing facilities. This chapter identifies a set of challenges that must be addressed by collaboration of research and operational agencies to advance weather and air quality research.
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Additional disasters were asso 4In1922, well before the advent of digital computing, Lewis Richardson published the visionary "Weather Prediction by Numerical Process," and with it the first true numerical weather forecast.
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Poor outdoor air quality, due to both gaseous and particulate matter (PM) constituents, contributes to millions of premature deaths annually worldwide and also negatively impacts agriculture yields and can degrade infrastructure.
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Space-based remote sensing provides essential measurements on the state of our atmosphere, notably by providing routine and consistent national observations for short-term forecasting (i.e., minutes to hours to several days) , as well as global measurements that are essential for medium
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Addressing the objectives and goals described in this chapter will contribute to societal benefits that range from information for short-term needs, such as accurate severe weather forecasts and air quality simulations that protect life and property, to improved monthly to subseasonal precipitation and temperature outlooks that anticipate extremes in heat, droughts, and flooding, to a longer-term scientific understanding necessary for future applications that will benefit society in ways still to be realized. Contextual Issues Our ability to simulate the past, current, and future state of the atmosphere has improved over the past decade (Bauer et al., 2015)
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Increased computer power and improved software engineering will enable data assimilation systems and forecasting models to move steadily toward exascale computing with commensurate higher fidelity, wider range of represented physical processes representation, increased temporal and spatial resolution, increased number of high-resolution ensembles, and longer lead times. Applications' demands will also require global high-resolution modeling and forecasting.
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provided wide areal coverage of • ocean-surface wind speed and direction that proved extremely valuable for atmospheric and ocean forecasts as well as nowcasting of extreme weather for many of the national agencies routinely identified in NASA's Senior Reviews. Although developed as a NASA research mission, QuikSCAT supplied data that were routinely assimilated into operational numerical weather forecast models.
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. • ver the last decade, the use of satellite data of air pollutants, such as OMI nitrogen dioxide O and OMI sulfur dioxide, for scientific research and health and air quality applications has grown dramatically.
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BOX 7.1 SATELLITES IN WEATHER FORECASTING Over the past 40 years the numerical weather prediction skill at the operational centers has steadily increased, and forecasts beyond 2 weeks are now seen as possible. These advances have been attributed to more accurate initial conditions owing to better data assimilation methods and more observational data (e.g., Vitart et al., 2014; Buizza and Leutbecher, 2015; NASEM, 2016)
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SOURCE: Met Office, U.K., private communication, June 2017. Another challenge is to bridge the gap between weather forecasts and seasonal outlooks to enable meaningful forecast skill that extends well into and through the subseasonal range of 2 weeks to 2 months.
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Convection and precipitation play a primary role in many high-impact weather events over a broad range of temporal and spatial scales (e.g., severe storms, tropical cyclones, floods, etc.)
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To improve the estimates of these fluxes and to better understand the interaction of atmospheric boundary layer with clouds and convection, better measurements from space of temperature, water vapor, and vector wind in the free troposphere and boundary layer are necessary. A big challenge in improving our understanding of clouds and precipitation is gaining insights into the processes that govern where precipitation forms and its intensity.
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Geostationary sensors provide high temporal resolution over a given hemisphere, while low-Earth orbiters provide global coverage with higher spatial resolution than if placed in geostationary orbits. Small satellites and CubeSats can provide opportunities to not only test new technologies and focus sampling strategies but also to fly low-cost missions and constellations.
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processes are integral to the air-surface (land, ocean, and W sea ice) exchanges of energy, momentum, and mass, and how do these impact weather forecasts and air quality simulations?
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In order to adequately represent the key boundary layer processes responsible for the exchange of energy, moisture, and pollutants between the surface and the free troposphere, high-resolution, diurnally resolved, 3D measurements of horizontal wind, temperature, humidity, and aerosol and trace gases are required. Measurement Objectives PBL processes show a strong diurnal cycle.
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, Raman lidars) , and through data assimilation using a meteorological model (including chemical processes)
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How can environmental predictions of weather and air quality be extended to seamlessly forecast Earth system conditions at lead times of 1 week to 2 months? There are increasingly more demands to extend operational environmental forecasts beyond the typical 7- to 10-day weather forecasts into useful multiweek subseasonal forecasts.
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The challenges include the following: • Improving the observations and data assimilation techniques to significantly reduce errors in the atmospheric initial state that amplify and propagate during the course of the forecast; • Developing accurate models and parameterizations of complex subgrid scale processes that have significant importance to subseasonal phenomena and predictability, including deep convection and mesoscale organization of storm systems, convective vertical mass transport and propagation of tropical potential energy into the midlatitudes, atmospheric boundary layer processes, aero sol-cloud-precipitation interactions, ocean mixed-layer and sea-ice processes, land-surface and land-atmosphere interactions involving root zone and surface soil moisture, snow processes and vegetation dynamics, stratosphere-troposphere interactions; • dentifying and characterizing sources of subseasonal predictability, including natural modes of I variability (e.g., ENSO, MJO, IOD, QBO) , slowly evolving Earth system components, and some elements of "external forcing" (e.g., annual phenological cycle, natural and anthropogenic emissions of aerosols)
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Advances across these areas require improved relevant global initial atmospheric, boundary layer, and surface conditions; and process understanding and assimilation/modeling capabilities of atmospheric convection, mesoscale storm organization, and atmosphere and ocean boundary layers, including surface characteristics. Space-based observations need to be complemented by in situ networks and research campaigns for synergistic use in process research, satellite measurement validation, and development and validation of subseasonal forecast models.
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Global Navigation Satellite System-Radio Occultation (GNSS-RO) provides soundings with excellent vertical resolution but inadequate horizontal resolution due to the occultation geometry.
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. These exchanges are critical to weather and climate prediction because the bulk of the interactions with solar heating and evaporation that drive the atmosphere and ocean take place in the boundary layer rather than the free atmosphere.
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. Local daily increases in surface fluxes of energy, moisture and air pollutant increase the exchange between the boundary layer and the free atmosphere, and impact weather and air quality locally and downwind (Song et al., 2009; Kilpatrick and Xie, 2015)
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Land-surface temperature can be determined from satellite IR radiometers complemented by modeling or microwave radiances. However, land temperature changes are highly dependent on cloud cover and FIGURE 7.3 Small spatial scale changes in surface characteristics that will influence local weather and heat and moisture budgets.
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A spatial resolution of 5 km could be achieved with relative cost-effectiveness by using Ka-band, with similar accuracy to the Ku-band used on prior U.S., Japanese, and Indian instruments. This higher resolution allows innovation while continuing the climate record.
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Subsurface salinity profiles are provided by in situ measurements. Near-surface air temperature and humidity can be usefully determined from microwave radiometry, provided there is a spectral channel sensitivity to sea-surface temperature (Bourassa et al., 2010; Jackson and Wick, 2010; Roberts et al., 2010; Smith et al., 2012)
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Why do convective storms, heavy precipitation, and clouds occur exactly when and where they do? Predicting the occurrence and location of convective storms, and how they evolve into severe weather, is critical for accurate forecasting of hazardous weather.
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These predictions are also integral to air quality forecasting, as convection can effectively ventilate pollutants in the planetary boundary layer to the free troposphere. Over the next decade, the resolution of weather and climate models will improve to explicitly represent cloud and convective processes.
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Current forecast models are unable to reproduce spatial patterns and frequency of precipitation events, which is critical for understanding the change in extreme weather events (Sun et al., 2007)
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in economic losses Atlanta Terra MODIS Aerosol Optical Depth (unitless) Suomi NPP VIIRS True Color Image November 10, 2016 November 10, 2016 Terra MODIS Aerosol Optical Seattle Depth (unitless)
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Objective W-5a. Improve the understanding of the processes that determine air pollution distributions and aid estimation of global air pollution impacts on human health and ecosystems by reducing uncertainty to <10 percent of vertically resolved tropospheric fields (including surface concentrations)
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, O3, and NO2 within the boundary layer and lower free troposphere can be best met by a combination of space-based observations, and expansion of aircraft and ground-based observations in conjunction with chemical transport modeling to capture surface levels. Current in situ networks have limited spatial and temporal coverage and do not capture the chemistry and transport that often occur above the boundary layer, but impact "nose-level" concentrations.
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For more detail on possible observing strategies for these important regions, see the Consolidated Science and Applications Traceability Matrix in Appendix B Connections and Linkages to Other Panels Air pollution distributions strongly depend on meteorological processes, so this science question/ objective connects to other science questions/objectives, such as Question W-1, within the Weather and Air Quality Panel.
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Connections and Linkages to Other Panels As air pollution variations and trends strongly depend on variations and trends in meteorology, so this science question/objective connects to other science questions/objectives, such as Question W-1, within the Weather and Air Quality Panel. In addition, it has connections to the Ecosystems subpanel, as air pollution degrades ecosystems viability and reduces crop yields, and to the Climate subpanel, as PM and O3 are climate forcers.
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and the recently launched Tropospheric Monitoring Instrument (TROPOMI) , give atmospheric O3 columns, which have very little information on the vertical distribution of O3 within the troposphere.
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For instance, satellite data of lightning distributions and temporal variations will be useful to infer the middle and upper tropospheric NOx lightning source, which is not currently reliably discerned in tropospheric column NO2 data. This is important, as lightning NOx is a major driver of tropospheric OH and also contributes to O3 formation in the free troposphere, where O3 is radiatively important.
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, the recently launched Tropospheric Monitoring Instrument (TROPOMI) , and the upcoming Geostationary Carbon Cycle Observatory (GeoCARB)
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An important step in better precipitation forecasts requires observations of the coupling between cloud water content, vertical mass fluxes, and precipitation yield; these are needed to develop new formulations for models operating at these fine spatial scales. As the computing power continues to increase, cloud resolving models now used in regional models will operate on global domains (Tao et al., 2017)
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can provide the needed profiles of temperature, moisture, and to a certain degree, winds at the required space and time scales in nonpolar regions. Measurement Approaches Observation of integrated ice mass, particle fall velocities, vertical air motions, and surface precipitation rates would satisfy a need to constrain precipitation efficiency, convective mass fluxes, and sedimentation rates in weather and global models.
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. Combined Doppler velocity with terminal fall speed estimates from mean particle size can be used to infer vertical air motions.
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They are essential both for model improvement (especially, subgrid-scale cloud representation) and for effective all-sky radiance data assimilation to improve global and regional short-range weather forecasts.
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Improvements in current forecast models along with the incorporation of observations within the data assimilation systems have been useful in providing appropriate weather guidance to decision makers. However, forecasting heavy precipitation remains a challenge, and without understanding the microphysical processes involved in convective growth, the simulation of the physics of a convective storm at a scale of 1-3 km is not possible.
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Improved 2-week prediction on the potential for extreme weather events such as tropical cyclones or severe convective storms (e.g., Brunet et al., 2010; Vitart et al., 2017; Vitart and Robertson, 2017) enabled by improved global observations, data assimilation, and Earth system prediction models will be critical for these longer range decision-making areas for the United States (NASEM, 2017)
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Bulletin of the American Meteorological Society 95:543-564. Banta, R.M., C.J.
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Bulletin of the American Meteorological Society 91(10)
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Bulletin of the American Meteorological Society 95(4)
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Bulletin of the American Meteorological Society August:1749-1752. L'Ecuyer, T.S., and J.H.
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. Bulletin of the American Meteorological Society 82:2749-2767.
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Project Database. Bulletin of the American Meteorological Society 98(1)
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Bulletin of the American Meteorological Society 94:1849 1870. Zhang, F., and G
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